Satellites in a geosynchronous orbit, located approximately 22,000 miles above the equator, may be used to provide one-way or two-way communications with a widely dispersed remote terminal population, some of which may be affixed to mobile assets. Communications transmissions from a central hub via satellite to the remote terminals are referred to as the forward link, while communications transmissions from the remote terminals via satellite to a central hub are referred to as the return link.
The amount of data that can be transmitted through a communication channel is limited by the bandwidth of the channel. Therefore, data compression methods and systems are useful for storing and transmitting large quantities of data. The more data is compressed, the greater the quantity of data can be transmitted over a communication channel. For example, the time required to transmit data is reduced when compression is used to decrease the number of bits of data to be transmitted, especially on communication channels with narrow bandwidth. Accordingly, data compression systems aim to effect savings in memory required to store the data or the amount of time (bandwidth) required to transmit the data. By decreasing the required memory for data storage or the required time for data transmission, compression results in monetary savings.
Data compression methods that compress data signals and decompress the compressed data signals back into the original data are known. For example, a conventional text data compression method is the Huffman Coding technique. In the Huffman Coding data compression technique, frequently used characters are assigned smaller codes than characters that are less frequently used. Since it is not possible to determine when one codeword ends and another starts, no complete code for any character can be the beginning of the code for another character. This leads to some quite long codewords for low probability characters. The Huffman method typically results in long coding sequences and is not suitable for satellite communication.